[Here's some more info on Birkeland Currents from the ThunderBolts Project Electric Universe website. You can see the whole chapter at the link at the bottom . . . SC]

7.1 Birkeland Currents

There is another cause of filamentation of currents in plasma. This is due to the fact that there is a force of attraction between any two parallel currents. By “parallel currents” we mean that the direction of flow or motion of like charges (say, the electrons, or the protons or ions) in one filament of matter in space is in the same or nearly the same direction in both of the two (or more, in some cases) filaments of current. Each current generates a magnetic field which circles the first current and attracts the second current according to the normal laws of electro-magnetism. Herefore the two currents are drawn together, as illustrated in this tutorial (courtesy of the National High Magnetic Field Laboratory website), and this short video of two current-carrying conductors and the forces induced between them, showing parallel currents and non-parallel currents, and the resultant forces (courtesy YouTube and MIT Physics Lecture Demonstration Group).”

This effect will apply to individual electron streams as well as to wires carrying currents. Therefore, in a plasma, a diffuse current will tend to become concentrated into a filament, as we have seen. Similarly, a sheet of current will also tend to coalesce into individual filaments, rather like a sheet of falling water breaks up into individual streams.

Braided current sheets glow softly in visible and infrared light along the Cygnus Loop of the Veil Nebula

If two parallel filaments occur in the same vicinity, or form out of a sheet of current due to the filamentation processes, then they will attract each other and initially move toward one another under under the magnetic attraction described by the Biot-Savart Law. Therefore there is a tendency for current cylinders to occur in pairs.

The inverse-distance dependency of the Biot-Savart force law between current-conducting filaments leads – curiously – to pairing of filaments. This shows 3 current filaments in a particle-in-cell (PIC) computer simulation, where only two will interact strongly while the third remains quiescent. This leads directly to “twoness” or “doubleness” when many filaments are present in a plasma with a significant magnetic field.

A point of balance is reached when the long-range attraction force is balanced by a shorter-range repulsion between the two counter-parallel spiraling currents’ azimuthal components. Analysis shows that there is an offset in the centers of the attractive forces that results in a couple, or force of rotation, acting on each current. The twin currents will therefore tend to spiral around a common axis in a helical motion. As before, the axis of the helix will tend to be aligned with the general magnetic field.

This arrangement of current pairs is known as a Birkeland Current after the Norwegian physicist Kristian Birkeland, who first studied them in the early part of the 20th Century.

7.2 Magnetic Ropes

The spiraling effect of currents around each other gives the appearance of twisted ropes . . .

[SNIP]